1. Field of the Invention
The invention relates to a method of monitoring the state parameters in a switching device, preferably monitoring a switch position, tripping causes and/or device faults, by recording and evaluating suitable signals, wherein sensors are used which can be influenced or disturbed by external electrical and/or magnetic fields. The invention also relates to an associated device for carrying out this method, wherein a switching device has associated devices for monitoring state parameters, such as a switch position, tripping causes and/or device faults. Sensors which are used for monitoring the state parameters can be influenced or disturbed by external electrical and/or magnetic fields.
International Publication WO 96 07 192 A2 discloses a switching device having devices for a state recognition or state detection. In such switching devices, for example circuit breakers, a suitable sensor equipment is able to record a wide variety of state parameters, such as the switch position xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d. In addition, it is also possible to record specific switching device tripping causes, such as xe2x80x9cshort circuitxe2x80x9d or xe2x80x9covercurrentxe2x80x9d and also general device faults, such as xe2x80x9cswitching contacts welded.xe2x80x9d An advantage here is that the sensors, inside their own sensor housing, can be placed at a suitable location, wherein the sensor housing can be coupled to a side of the switching device housing, for example, and that neither a mechanical or optical operative connection nor an electrical line connection from the switching device housing and/or the line conductors connected thereto must be led into the interior of the sensor housing. In this case, it is desired, in the context of switchgear devices which are able to communicate, to allow a processing and central reporting of the monitored and recorded switching states via a bus system, for example.
The devices used in practice to date for a switchgear monitoring, for example auxiliary switches and fault signal switches in line circuit breakers or short-circuit indicator switches in circuit breakers, operate entirely electromechanically and are consequently not susceptible to electromagnetic interference influences. At the most, problems arise here only from converting the electrical contact signals into bus-compatible and electronics-compatible control signals. However, if specific electrical sensors are used, then, based on the sensors used, there is a different fault or interference characteristic, depending on the sensor principle. These electrical sensors must be protected against a respective specific interference.
It is accordingly an object of the invention to provide a method of monitoring state parameters and an associated device for performing the method which overcome the above-mentioned disadvantages of the heretofore-known methods and devices of this general type and which ensure a reliable indication of the switching state.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of monitoring a switching device, which includes the steps of:
monitoring state parameters in a switching device by recording and evaluating sensor signals of sensors susceptible to an interference caused by at least one of an external electrical field and an external magnetic field;
determining whether the sensor signals are disturbed signals or undisturbed signals by evaluating a temporal sequence of the sensor signals; and
suppressing the interference in the sensor signals by generating evaluation signals corresponding to the undisturbed signals.
In accordance with another mode of the invention, the step of monitoring the state parameters in the switching device includes monitoring a switch position, a tripping cause and/or a device fault.
In accordance with yet another mode of the invention, the evaluation signals are decoupled from an interference produced by the switching device and/or from the interference caused by the external electrical or magnetic field.
In accordance with a further mode of the invention, the evaluation signals are electronically processed.
In accordance with yet a further mode of the invention, the evaluation signals are checked for plausibility. The evaluation signals are discriminated from signal patterns caused by the interference.
In accordance with another mode of the invention, the sensors record steady-state signals and transient signals of switching states of the switching device. A state signal is derived from each of the steady-state signals by electronically processing the steady-state signals. The state signal follows a state change after a given time interval if a new state remains unchanged within the given time interval. An interference-suppressed steady-state signal is then formed. A further state signal is derived from each of the transient state signals, actuated by slow actuators, such as a bimetallic strip, by electronically processing the transient state signals. The further state signal follows a state change after a given time interval if a new state remains unchanged within the given time interval. An interference-suppressed transient state signal is then formed. The transient state signals of fast actuators are logically combined with the interference-suppressed steady-state signals and with the steady-state signals not subjected to interference suppression. As a result of the combining step, at least one of the steps of enabling a signal path of a transient state signal, disabling the signal path of the transient state signal, permanently storing the transient state signal after being temporarily stored, and erasing the transient state signal after being temporarily stored is selectively performed.
In accordance with an added mode of the invention, transient state signals, such as a short-circuit tripping, are assessed selectively as a state signal being unaffected or as being affected by the interference by using a defined temporal signal pattern of sensor signals. If the state signal affected by the interference has been recognized, at least one of the steps of disabling the signal path and erasing the transient state signal after being temporarily stored is performed for deriving interference-suppressed transient state signals from the transient state signals.
In accordance with another mode of the invention, the interference-suppressed transient state signals, such as an overcurrent tripping signal and/or a short-circuit tripping signal, are stored and only a superordinate interference-suppressed transient signal, such as the short-circuit tripping signal, is indicated.
According to a preferred embodiment of the method according to the invention, the steady-state and non-steady-state, i.e. transient, signals are advantageously processed such that undisturbed signals are generated from the disturbed signals for a further evaluation. In the corresponding device according to the invention, there are devices or measures for passive interference suppression, on the one hand, and active interference suppression, on the other hand, for this purpose.
The devices or measures for the passive interference suppression are preferably suitable shielding measures, while the devices for active interference suppression preferably operate electronically. Advantageously, the combination of passive interference suppression with active interference suppression can then end interference events with a sufficient intensity within a predetermined time interval.
In the context of the invention, it is possible for the state parameter changes recorded by the sensor equipment to be temporarily stored and, if a fault is recognized within a predeterminable time interval, for the old values of the state parameters to be retained. This ensures that, in a further communication, no incorrect statements about state parameters are processed.
A particularly advantage of the invention is that the possibility of combining passive and active interference suppression allows a selective assessment of the characteristic processes. This advantage applies both, for the simple and reliable interference suppression in stationary sensor signals and for the complex form of the interference suppression in the transient sensor signals. Thus, considerable progress is made in comparison with the previously used concepts working with reflection light barriers. Interference suppression in sensor circuits for applications in the switching technology will become particularly significant in the future.
With the objects of the invention in view there is also provided, in combination with a switching device having state parameters, a device for monitoring the state parameters, including:
sensors for recording sensor signals significant for a switching state, the sensors being susceptible to an interference caused by at least one of an external electrical field and an external magnetic field;
an evaluator connected to the sensors for evaluating a signal sequence of the sensor signals and for determining if the sensor signals are affected by the interference;
a passive interference suppression device associated with the sensors for a passive interference suppression; and
an active interference suppression device, such as an electronic circuit, connected to the evaluator generating evaluation signals corresponding to the sensor signals in a state unaffected by the interference for an active interference suppression.
In accordance with another feature of the invention, the sensors record the sensor signals significant for the switching state corresponding to a switch position, a tripping cause, and/or a device fault.
In accordance with yet another feature of the invention, the passive interference suppression device is a shield for shielding the sensors against the external electrical field and/or the external magnetic field. The shield preferably includes shielding plates made of a ferromagnetic material and/or a nonferromagnetic material with a high electrical conductivity.
In accordance with a further feature of the invention, the electronic circuit recognizes an occurrence of a disturbance of the sensors by recognizing a predefined faulty signal pattern of the sensor signals.
In accordance with another feature of the invention, the electronic circuit evaluates a signal pattern by evaluating current sensor signals and/or temporal courses of the sensor signals.
In accordance with an added feature of the invention, the passive interference suppression device together with the active interference suppression device terminate interference events with a sufficient strength within a given time interval.
In accordance with yet another feature of the invention, the evaluator temporarily stores changes of the state parameters and retains old values of the state parameters, if a fault is recognized within a given time interval.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method of monitoring state parameters in a switching device, and an associated device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.